A common type of shutter mechanism for closing a door opening comprises a plurality of shutter members such as parallel plates or blades extending across the opening and movably mounted to opposite sides thereof. In a closed position of the shutter, the blades lie generally in the plane of the opening, with touching or overlapping edges, thereby closing the opening. In an open position of the shutter, the blades are removed from the opening and may be stacked one over the other or collapsed face-to-face or rolled in a roll or just drawn away along the ceiling or a wall, etc. as the design may be. The transition from closed to open position and back is performed by a motion device that may employ pulleys and ropes or chains, scissors lever mechanism, motion screw, etc. and a motor or manual drive. Another common type of shutter has a number of parallel bars connected with transverse elements such as diagonal cross-bars moveable like scissors, or flexible chains, bands, etc. so that these elements obstruct the passage when the parallel bars are in the most spaced position.
For example, U.S. Pat. No. 5,163,494 discloses a sectional door installation comprising a series of horizontal blades mounted with their opposite ends to scissors linkages. The lowermost linkage is raised or lowered by an endless chain whereby all linkages contract or extend simultaneously. The blades are mounted to one of the two levers in a scissors pair and turn together with the lever, so that in the most raised position, the blades are nearly horizontal and are stacked in a tight stack under the upper beam of the doorframe.
U.S. Pat. No. 5,469,905 describes a security and hurricane shutter using blades which are longitudinally pivoted to each other. Every other pivoting axis is supported in a vertical guide at the two opposing sides of the door. The shutter can use either pulleys or motion screw that raises the lowermost blade. Thereby, the whole blade assembly collapses like accordion towards the upper beam of the door.
U.S. Pat. No. 4,846,244 discloses a window shutter comprising a plurality of horizontal blades, a tilting device for simultaneously tilting all the blades about their horizontal axes, and a raising device. The blades are mounted on shafts received within channels at opposite sides of the window. The devices for tilting and raising of the blades employ ropes and pulleys like in Venetian blinds.
The usage of motion screws in shutter mechanisms generally allows more accurate motion than the usage of ropes or chains. However, the stacking of the blades in known shutter mechanisms requires that only one blade is engaged with the screw thread thus overloading this blade while the other blades lose the accuracy of motion.